Middlesbrough-born renegade MI5 agent David Shayler was today learning if the highest court in the land has upheld his right to use certain defences in his forthcoming Old Bailey trial.

Law Lords were due to deliver their ruling at the House of Lords this afternoon.

Mr Shayler is accused of disclosing State secrets in 1997 in a series of newspaper articles about alleged illegal activities and incompetence in the security services.

The Court of Appeal ruled last November that he was unable to use a "public interest" defence in his trial, nor was he able to argue a defence of "necessity" - in other words, that he had been compelled to reveal secret information to expose wrongdoing.

Mr Shayler, who now lives in London, said: "What's at stake here is the rights of the citizen to be able to report crimes committed by the State to the police, to the Government or to the media - which is prevented by the Official Secrets Act.

"One of the things we may score highly on with the Lords is that the Attorney General is ordering the prosecution on me and is also a member of the Government. That is a clear conflict of interest.

"I think we've got a very good chance."

His legal team argued at a hearing last month that the Official Secrets Act was incompatible with the Human Rights Act unless it contained a guarantee on a right to "freedom of expression".